Introduction

Computational Fluid Dynamics (CFD) is an enormously rich field on its own. Originally covered by the finite difference method, the CFD field equations are nowadays usually solved by the finite volume method. Occasionally one also encounters finite element CFD codes. Whereas the finite element method can be considered as a code for which the primary variables (i.e. the variables solved for in the ensuing linear equation system such as the displacements) are determined at the nodes and the secondary variables (derived from the primary ones by differentiation, such as the strains) at the integration points, the finite volume method is characterized by the primary variables (such as velocity, static temperature, static pressure... in CFD calculations) being determined at the center point of the elements (usually called cells). Thus, the size of the equation system corresponds to the number of elements. In what follows frequent recourse will be taken to references [61] and [22]